Q. 45.0( 1 Vote )
A closed vessel is half filled with water. There is a hole near the top of the vessel and air is pumped out from this hole.
A. The water level will rise up in the vessel.
B. The pressure at the surface of the water will decrease.
C. The force by the water on the bottom of the vessel will decrease.
D. The density of the liquid will decrease.
The water in the vessel is half down by gravity. To make it rise in the vessel, we need an additional force opposing the gravity. The pumping of air does not provide this force, hence option (A) is untrue.
As the air is pumped out, the number of air molecules decreases and hence the pressure decreases. Option(B) is therefore correct.
The force on the bottom of the vessel is due to the weight of the water and the pressure due to air. As it is pumped out, the total force on the bottom of the container decreases. This makes option (C) correct.
Changing air pressure does not affect the density of the liquid. Hence, option (D) is wrong.
Rate this question :
The weight of an empty balloon on a spring balance is W1. The weight becomes W2 when the balloon is filled with air. Let the weight of the air itself be ω. Neglect the thickness of the balloon when it is filled with air. Also neglect the difference in the densities of air inside and outside the balloon.HC Verma - Concepts of Physics Part 1
A solid float in a liquid in a partially dipped position.HC Verma - Concepts of Physics Part 1
(a) Pressure decreases as one ascends the atmosphere. If the density of air is ρ, what is the change in pressure dp over a differential height dh?
(b) Considering the pressure p to be proportional to the density, find the pressure p at a height h if the pressure on the surface of the earth is p0.
(c) If p0 = 1.03×105 N m-2, ρ0 = 1.29 kg m-3 and g = 9.8 m s-2, at what height will the pressure drop to (1/10) the value at the surface of the earth?
(d) This model of the atmosphere works for relatively small distances. Identify the underlying assumption that limits the model.
Physics - Exemplar
An ideal fluid flows through a pipe of circular cross-section made of two sections with diameters 2.5 cm and 3.75 cm. The ratio of the velocities in the two pipes isPhysics - Exemplar
Streamline flow is more likely for liquids withPhysics - Exemplar
Pressure is a scalar quantity becausePhysics - Exemplar
If water be used to construct a barometer, what would be the height of water column at standard atmospheric pressure (76 cm of mercury)?HC Verma - Concepts of Physics Part 1
Find the force exerted by the water on a 2 m2 plane surface of a large stone placed at the bottom of a sea 500 m deep. Does the force depend on the orientation of the surface?HC Verma - Concepts of Physics Part 1
Suppose the glass of the previous problem is covered by a jar and the air inside the jar is completely pumped out. (a) What will be the answers to the problem? (b) Show that the answers do not change if a glass of different shape is used provided the height, the bottom area and the volume are unchanged.HC Verma - Concepts of Physics Part 1
Water level is maintained in a cylindrical vessel up to a fixed height H. The vessel is kept on a horizontal plane. At what height above the bottom should a hole be made in the vessel so that the water stream coming out of the hole strikes the horizontal plane at the greatest distance from the vessel (figure 13-E11)?
HC Verma - Concepts of Physics Part 1